1. Field of the Invention
The invention relates to endoscopic surgical tools. More particularly, the invention relates to an elastomeric seal between the push rod and outer tube of endoscopic instruments such as laparascopic instruments.
2. State of the Art
Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic surgery involves one or more incisions made by trocars where trocar tubes are left in place so that endoscopic surgical instruments may be inserted through the tubes. A camera, lens, or other viewing device is often inserted through one trocar tube, while a cutter, dissector, or other surgical instrument is inserted through another trocar tube for purposes of manipulating and/or cutting the internal organ. Sometimes it is desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, organ or tissue may be grasped with one surgical instrument, and simultaneously may be cut with another surgical instrument; all under view of the surgeon via the viewing device in place in one of the trocar tubes.
Trocar tubes are usually provided with a proximal elastomeric seal to prevent gas and other fluids from escaping from the body cavity while allowing endoscopic instruments to be inserted through the trocar tubes. These seals are only partially effective, however, because of the nature of the endoscopic instruments used. In particular, most endoscopic instruments include a hollow outer tube, a push rod which extends through the tube, and an actuating means engaging the tube and the push rod. The actuating means imparts reciprocal axial motion to the push rod, and hence to the end effectors (cutters, grippers, dissectors, etc.) which are coupled to the push rod and the tube, such that the end effectors are moved. When inserted through a trocar tube, the endoscopic instrument tube is surrounded by the elastomeric seal of the trocar tube. This prevents gas and other fluids from escaping through the annular space between the instrument tube and the trocar tube. The inventor has realized, however, that the annular space between the push rod and the instrument tube still presents a clear, albeit small, path for fluids, and that is why the proximal trocar tube seal is only partially effective. Gas and other fluids can enter the endoscopic instrument tube and pass through to the actuating means. The escape of gas can desufflate the surgical site requiring additional insufflation of gas.